This invention relates to a method and an apparatus for attaching a belt-shaped member, for example, a tread rubber as a constituent member of a pneumatic tire to a forming drum.
Various methods and apparatuses for attaching belt-shaped members have been known, for example, disclosed in Japanese Patent Application Laid-open No. 62-236,728. In the known method, after measuring the length of a belt-shaped member cut in a length substantially equal to the circumferential length of a forming drum, the front end of the belt-shaped member is grasped by grasping means which is then moved to the forming drum to pressure-join the front end of the member with it. Thereafter, the belt-shaped member is supplied to the forming drum, during which the drum is being rotated so that the belt-shaped member is attached to the forming drum around approximately three fourths of its circumference. The grasping means is then returned to the rear end of the belt-shaped member.
The rear end of the belt-shaped member is then grasped by the grasping means which is then moved to the forming drum so as to attach the remaining portion of the belt-shaped member to the rotating forming drum to join the front and rear ends of the belt-shaped member with each other. In the method and apparatus, the supplied speed of the belt-shaped member is made different from the circumferential speed of the forming drum in attaching the remaining portion to the forming drum so that the belt-shaped member is elongated or contracted to bring the length of the attached belt-shaped member into a coincidence with a predetermined length, for example, one circumferential length of the forming drum.
In addition, a method and an apparatus have been known which was disclosed in Japanese Patent application Laid-open No. 1-303,163. In the method and apparatus, after the front end and the rear end of a belt-shaped member cut in a length substantially equal to the circumferential length of a forming drum are grasped by front end grasping means and rear end grasping means, respectively, these front and rear end grasping means with the grasped belt-shaped member are moved in synchronism with each other to plate-shaped transfer means to transfer the belt-shaped member to a position above the plate-shaped transfer means where the front and rear grasping means are moved away from each other to eliminate any loose portion or slack of the belt-shaped member. After the belt-shaped member is held by suction on plate-shaped transfer means, it is moved to the forming drum to attach the belt-shaped member to the circumference of the forming drum.
In the former method and apparatus, however, as only one grasping means is adapted to grasp both the front and rear ends of the belt-shaped member, the moving distances of the grasping means unavoidably become long. As a result, the cycle time for attaching the belt-shaped member to the forming drum is prolonged. Moreover, the adjustment of length of the belt-shaped member is performed with the remaining portion of the belt-shaped member or one fourth of its overall length. Therefore, the relevant portion is locally elongated or contracted so that the thickness or width of the portion is greatly changed to lower the quality of produced tires.
In the latter method and apparatus, after the belt-shaped member has been once transferred onto the plate-shaped transfer means, the belt-shaped member is supplied from the transfer means to forming drum. Therefore, the apparatus is complicated in construction and the operation becomes troublesome. Moreover, the measurement and modification of the lengths of belt-shaped members are not considered in the latter method and apparatus. Therefore, if a belt-shaped member is cut with an error in length, its front and rear ends may be incompletely joined due to the error.